The construct of いつの間にか

Question

In Japanese, we can add か to question words to make it mean "some-xxx." Example:

• 何 what 何か something
• 誰 who 誰か somebody
• 何人 how many people 何人か some amount of people (何人かの友達きた some friends came)
• 幾つ how many 幾つか some amount of xxx (いくつかの季節を歩んだ walked through some seasons)
• いつ when いつか sometime
• いつの日 which day いつの日か someday

I had always thought that か is now "sticked" to the question word and they should be viewed together as one whole thing. However, when I saw the phrase いつの間にか or いつの日にか, I was surprised to see the か being split from いつの日, for I'd totally expected いつの日かに, to mean "at someday (in the future)." (i.e. I'd expected いつの日かにやめるかな rather than いつの日にかやめるかな), since I thought 「いつの日か」 is one integral part.

When writing this question, I realized that I've been saying 誰にも/誰とも instead of 誰もに/誰もと, however I say 誰かに instead of 誰にか. I unconsciously learned these and had been using them without ever questioning them, until now I find myself never having really understood the grammar behind adding か/も to question words, and what happens when particles like に and と are involved.

If I wanted to say "I'll give it to some friends", I know that 何人かの友達にあげる is correct, but why is 何人の友達にかあげる wrong(yet we say いつの日にか)?

If I wanted to say "I'll give it to however many friends!", I know that 何人の友達にもあげる is correct, but why is 何人もの友達にあげる or 何人の友達もにあげる wrong?

All of these seem way too random for me. What are the rules behind them?

質問長くてすみません。日本語を勉強するには、たくさんの音楽を聴いたり動画を見たりして、教科書を読むのは少ないです。正しい言い方はどんどん見習ったのにそのうちの文法はまだ分かりません。ぜひ教えてください。

Answer 1

We have similar pairs of expressions depending on whether か comes right after or before a particle:

• どこからか out of nowhere / from who-knows-where
• どこかから from somewhere
• どこへか to who-knows-where
• どこかへ to somewhere
• いつからか since who-knows-when
• いつかから since some/certain time point
• 誰からか from who-knows-who / I can't remember who but, ...
• 誰かから from someone

I'm not sure if these are the best English translations, but my point is that the expression with "interrogative + particle + か" carries a stronger nuance of "I'm wondering but I don't know", compared to expressions like 誰か/どこか, which, as you mentioned, simply translate to someone/somewhere/etc. They do not necessarily imply that the speaker is wondering.

Both patterns are useful and should be mastered separately. But the "interrogative + particle + か" pattern is less common, and sounds slightly literary or bookish to me. いつの日かに and いつの日にか are semantically almost the same, but the latter sounds more sophisticated and dramatic to me. Practically, いつの間にか and いつの日にか can be remembered as a set expression.

As for "give it to some friends":

• 何人の友達にかあげる: This sounds strange because 何 and か are too far apart.
• 何人かにあげる: Natural.
• 何人にかあげる: Makes sense only when you want to emphasize the nuance of "I don't know how many but...". But this may be too stilted in speech, anyway.

Answer 2

I think to some extent the particle order is explainable by 'what phrases are naturally required by verbs'. (Maybe it's not the whole question of yours and there are certain 'counterexamples' though).

To put it simply あげる takes an indirect object, and requires a に-phrase. Hence 何人かに and not 何人にか.

か is a 副助詞 and makes an adverbial phrase.

For illustration, consider

1. 日取りをいつの日かに決めてほしい
2. 日取りをいつの日にか決める

1 is not completely natural, but いつの日か (which day) is felt as the object of 決める (literally: I want you to fix the date to which(ever) day) whereas 2 (semantically a bit odd) means 'I will decide the date some day', where いつの日にか works adverbially on 決める (i.e. I will fix the date some day (in the future)).

いつの日か is mostly used in the same way as 2 above, hence いつの日にか appears much more often while いつの日かに is not totally impossible. On the other hand, many verbs like あげる requires に-noun-phrase, hence に encapsulates the 'some'-phrase.